1. Field of the Invention
The present invention relates generally to a fluid-filled vibration damping device that exhibit vibration damping effect on the basis of flows of a non-compressible fluid filled therein. More particularly, the present invention is concerned with a pneumatically controlled fluid-filled vibration damping device that is capable of controlling its vibration damping characteristics by suitably changing an air pressure applied from an external air source to an air chamber formed in the vibration damping device, and that is suitably adoptable as an engine mount for use in an automotive vehicle.
2. Description of the Related Art
JP-A-10-339350 discloses a known example of a fluid-filled vibration damping device in which a first mounting member and a second mounting member are disposed in a mutually spaced apart relationship with each other, and are elastically connected with each other by an elastic body interposed therebetween, while a partition member is supported by the second mounting member so that a primary fluid chamber and an equilibrium chamber, which are both filled with a non-compressible fluid such as water, are formed on both sides of the partition member and held in fluid communication with each other via an orifice passage. The disclosed fluid-filled vibration-damping device is able to exhibit vibration damping effect on the basis of flows of the fluid through the orifice passage, upon application of a vibrational load between the first and second mounting members.
For assuring further improved damping effect, it has been proposed to modify the fluid-filled vibration damping device such that the pressure-receiving chamber is partially defined by a movable member disposed in a displaceable or deformable manner, and a working air chamber is formed by and between the movable member and the partition member. This proposed modification makes it possible to control vibration-damping characteristics of the fluid-filled vibration-damping device according to input vibrations. Namely, a suitable air pressure variation whose frequency corresponding to that of the input vibrations is applied to the working air chamber, so that the modified fluid-filled vibration-damping device can actively offset or absorb input vibrations with the help of the air pressure variation applied to the working air chamber, for example, thereby actively controlling fluid pressure variation in the pressure-receiving chamber. Alternatively, the modified fluid-filled vibration-damping device is capable of controlling its passive vibration damping effect. Namely, the tuning frequency of the orifice passage may be desirably changed by suitably changing the air pressure level in the working air chamber so as to adjust wall spring characteristics of the movable member, i.e., the pressure-receiving chamber.
As disclosed in the aforementioned JP-A-10-339350, the conventional fluid-filled vibration damping device has a structure in which the second mounting member is formed of a generally cylindrical metallic member. One of axially opposite open-end of the second mounting member is fluid-tightly closed by a flexible rubber layer, and a artition member is press-fitted and fixedly disposed in a bore of the second mounting member. The other open-end of the second mounting member is fluid-tightly closed by the elastic body with the other open-end of the second mounting member being press-fitted onto a metallic sleeve that is bonded to an outer circumferential surface of the elastic body upon vulcanization of a rubber material to form the elastic body. Thus, a fluid-tightly closed interior space of the second mounting member is divided into two chambers, i.e., a pressure-receiving chamber partially defined by the elastic body and an equilibrium chamber partially defined by the flexible rubber layer, which are both filled with a non-compressible fluid.
However, the conventional fluid-filled vibration damping device constructed as described above inevitably requires a relatively large axial length of the second mounting member in order to receive the partition member in its bore. This makes it cumbersome to manufacture the second mounting member, pushing up a manufacturing cost. Also, the relatively long cylindrical second mounting member makes it difficult not only to assemble the partition member into the bore of the second mounting member, but also to bond the flexible rubber layer to the one open-end of the second mounting member in a process of vulcanization of a rubber material to form the flexible rubber layer, resulting in low manufacturing efficiency. In addition, since the other open-end of the second mounting member is press-fitted onto the metallic sleeve bonded to the outer circumferential surface of the elastic body, the conventional fluid-filled vibration damping device does not assure a sufficient bonding strength in its axial direction.
Moreover, the conventional fluid-filled vibration damping device generally has a specific structure for permitting a connection of a port of an air passage formed through the partition member with an external air conduit, as disclosed in the aforementioned document No. JP-A-10-339350. Namely, the second mounting member is formed with a window formed through its cylindrical wall portion so that the port of the air passage is open to the external area through the window of the second mounting member. In general, the second mounting member is subjected to a drawing operation, e.g., all directional drawing, after being mounted onto the partition member so that the second mounting member is radially inwardly drawn onto and fixedly mounted onto the partition member. In the drawing operation, the presence of the window formed through the cylindrical wall portion of the second mounting member may cause a local decrease in strength of the second mounting member. This is prone to cause irregular deformation of the second mounting member, leading to an undesirable leakage of the non-compressible fluid through the interface between the partition member and the second mounting member. Thus, the conventional fluid-filled vibration-damping device suffers from difficulty in assuring a sufficient fluid-tight sealing with high stability.
Further, in the aforementioned drawing operation, it is required to precisely position the air port of the air passage formed in the partition member and the window of the second mounting member relative to each other, making it cumbersome to assemble the second mounting member and the partition member, resulting in a low manufacturing efficiency.
It is therefore one object of this invention to provide a pneumatically controlled fluid-filled vibration damping device, which is novel and simple in structure, which is easy to manufacture, and which assures high fluid-tight sealing in a pressure-receiving chamber and an equilibrium chamber.
The above and/or other objects of this invention may be attained according to at least one of the following modes of the invention. Each of these modes of the invention is numbered like the appended claims and depending from the other mode or modes, where appropriate, to indicate possible combinations of elements or technical features of the invention. It is to be understood that the principle of the invention is not limited to these modes of the invention and combinations of the technical features, but may otherwise be recognized based on the teachings of the present invention disclosed in the entire specification and drawings or that may be recognized by those skilled in the art in the light of the present disclosure in its entirety.
(1) A fluid-filled vibration-damping device for connecting two members in a vibration damping fashion, which includes (a) a first mounting member adapted to be fixed to one of the two members; (b) a second mounting member adapted to be fixed to an other one of the two members and having a cylindrical portion, while being disposed relative to the first mounting member such that one of axially opposite open-end portions of the cylindrical portion of the second mounting member is opposed to the first mounting member with an axial spacing therebetween; (c) an elastic body elastically connecting the first mounting member and the second mounting member with an outer circumferential surface thereof being bonded to the cylindrical portion of the second mounting member; (d) a first partition member fixedly supported by the cylindrical portion of the second mounting member so as to form at one of axially opposite sides thereof a pressure-receiving chamber partially defined by the elastic body and at an other one of axially opposite sides thereof an equilibrium chamber partially defined by a flexible layer. The pressure-receiving chamber and the equilibrium chamber are filled with a non-compressible fluid, and are held in fluid communication with each other through a first orifice passage at least partially defined by the first partition member. The fluid-filled vibration-damping device further includes (e) a movable member partially defining the pressure-receiving chamber and being supported by the first partition member in a movable manner, (f) a working air chamber defined by and between the movable member and the first partition member and being open to an external area through an air passage formed through the first partition member, and (g) a fixing member having a fixing sleeve portion and fixedly assembling a peripheral portion of the flexible layer to the first partition member. In this fluid-filled vibration-damping device, the first partition member includes a first fixing groove and a second fixing groove, which are axially spaced apart from each other and open in an outer circumferential surface of said first partition member, while extending in a circumferential direction of said first partition member. Also, the first partition member is assembled with the second mounting member such that the cylindrical portion of the second mounting member is fixedly disposed radially outwardly on one of axially opposite end portions of the first partition member with an other one of axially opposite open-end portions of the cylindrical portion thereof being press-fitted into the first fixing groove of said first partition member, and is assembled with the fixing member such that the fixing sleeve portion of the fixing member is fixedly disposed radially outwardly on the other one of axially opposite end portions of the first partition member with one of axially opposite open end portions of the fixing sleeve portion being press-fitted into the second fixing groove of the first partition member. In this fluid-filled vibration-damping device, the air passage is open in an axially intermediate portion of the outer circumferential surface of the first partition member, which is axially interposed between the first and second fixing grooves and exposed to an atmosphere, such that an opening of the air passage is connectable to an external air conduit.
In the fluid-filled vibration damping device according to this mode of the invention, the fixing member by which the peripheral portion of the flexible layer is fixedly assembled with the first partition member, is formed independently of the second mounting member to which the elastic body is bonded. This arrangement makes it possible to directly bond the elastic body to the cylindrical portion of the second mounting member in the process of vulcanization of the rubber material to form the elastic body, without needing the conventionally required metallic sleeve. Therefore, the present fluid-filled vibration-damping device is made simple in construction and is able to exhibit improved bonding strength and durability between the elastic body and the second mounting member, in comparison with the conventional fluid-filled vibration damping device in which the elastic body is indirectly bonded to the second mounting member such that the elastic body is bonded to the metallic sleeve upon vulcanization of the rubber material to form the elastic body, and then the second mounting member is press-fitted onto the metallic sleeve.
In the present fluid-filled vibration damping device, the axially intermediate portion of the outer circumferential surface of the first partition member is exposed to the atmosphere, and the opening of the air passage is formed so as to be located on the intermediate portion of the outer circumferential surface of the first partition member. This arrangement makes it possible to eliminate the conventional need for forming windows through the cylindrical portion of the second mounting member, which is fixedly mounted on the first partition member so as to seal the pressure-receiving chamber and the equilibrium chamber, and the fixing sleeve portion of the fixing member. Therefore, the cylindrical portion of the second mounting member and the fixing sleeve portion of the fixing member can be fixed to the first partition member with excellent fluid-tightness and stability, thus assuring high fluid-tight sealing at the pressure-receiving chamber and the equilibrium chamber with high reliability.
Since the second mounting member and the fixing member are formed independent of each other in the present fluid-filled vibration-damping device, these two members can be made small in their axial length. This makes it possible to reduce the number of manufacturing steps, in the case where the second mounting member and the fixing member are formed of metal by pressing, for example. Thus, the second mounting member and the fixing member can be manufactured with improved efficiency.
Preferably, the cylindrical portion of the second mounting member and the fixing sleeve portion of the fixing member are provided with engaging hooks at their open end portions, before these members are assembled with the first partition member. Namely, one of axially opposite open-end portions of the cylindrical portion of the second mounting member is bend radially inwardly over its entire circumference to form the engaging hook. Likewise, one of axially opposite open-end portions of the fixing sleeve portion of the fixing member is bend radially inwardly over its entire circumference. Then, these open-end portions provided with the engaging hooks of the cylindrical portion of the second mounting member and the fixing sleeve portion of the fixing member are mounted onto the axially opposite end portions of the first partition member, respectively. The second mounting member and the fixing member, which are assembled with the first partition member as described above, are then subjected to a suitable drawing operation to be drawn onto the first partition member, so that the engaging hooks of the second mounting member and the fixing member are press-fitted into the first and second fixing grooves, respectively. A variety of methods may be employed to form the engaging hook at the open-end portion of the second mounting member or the fixing member. For instance, the second mounting member or the fixing member may be formed of a metallic plate by drawing into a cylindrical cup shaped member, and then the central area of the bottom wall portion of the formed second mounting member or the fixing member is cut off by punching. This makes it possible to integrally form the engaging hook at the open-end portion of the second mounting member and the fixing member, simultaneously.
The movable member may be formed by a rubber elastic body having a suitable thickness, for example. Preferably, a peripheral portion of the movable member is fluid-tightly bonded to the first partition member. This arrangement makes it possible not only to transmit a pressure change in the working air chamber to the pressure-receiving chamber with high efficiency, but also to exhibit a desired fluid-tight sealing of the working air chamber with ease. In the present mode of the invention, the movable member may be formed of a rubber elastic body having a suitable thickness. In this case, elastic deformation of the movable member should be interpreted as the displacement of the movable member. A variety of structures may be employed to fix the peripheral portion of the flexible layer to the first partition member. Preferably, the following mode (2) or (3) may be employed to this end.
(2) A fluid-filled vibration-damping device according to the above-indicated mode (1), wherein the fixing member has a cylindrical configuration, and the peripheral portion of the flexible layer is bonded to the fixing member upon vulcanization of a rubber material to form the flexible layer. This arrangement makes it possible to reduce the number of component and to simplify the structure of the device, effectively.
(3) A fluid-filled vibration-damping device according to the above-indicated mode (1), further includes an annular metallic member formed independently of the fixing member. In this device, the peripheral portion of the flexible layer is bonded to the annular metallic member, while the annular metallic member is fixed to the first partition member via the fixing member.
(4) A fluid-filled vibration-damping device according to any one of the above-indicated modes (1)-(3), wherein the first partition member has a first recess open to the one of axially opposite sides thereof in which the pressure-receiving chamber is formed, and the movable member fluid-tightly closes an opening of the first recess so that the working air chamber is formed by and between the first recess and the movable member. According to this mode of the invention, the first partition member can effectively provide a space for forming the working air chamber.
(5) A fluid-filled vibration-damping device according to any one of the above-indicated modes (1)-(4), wherein the first partition member has a second recess open to the other one of axially opposite sides thereof in which the equilibrium chamber is formed, and partially defining the equilibrium chamber, and at least one of the opening of the air passage and the first orifice passage is formed in a peripheral portion of the second recess. According to this mode of the invention, the first partition member can effectively provide a space for forming the equilibrium chamber with a sufficient volume, and a space for forming at least one of the openings of the air passage and the first orifice passage as well, at the peripheral portion of the second recess.
(6) A fluid-filled vibration-damping device according to any one of the above-indicated modes (1)-(5), wherein the axially intermediate portion of the outer circumferential surface of the first partition member has a recess, and the opening of the air passage comprises a cylindrical port protruding from a bottom surface of the recess into an inside the recess. The cylindrical port is connectable with the external air conduit. In the fluid-filled vibration-damping device according to this mode of the invention, the protruding cylindrical port is housed within the recess, thus improving manufacturing efficiency. Namely, the presence of the recess formed around the cylindrical port makes it easy to connect the external air conduit with the cylindrical port, while effectively preventing the cylindrical port from being damaged during manufacture or shipment of the fluid-filled vibration-damping device.
(7) A fluid-filled vibration-damping device according to any one of the above-indicated modes (1)-(5), wherein the opening of the air passage comprises a cylindrical port that is formed on and protrudes from the axially intermediate portion of the outer circumferential surface of the first partition member, and that is connectable with the external air conduit. In the fluid-filled vibration-damping device according to this mode of the invention, the cylindrical port can be connected with ease with the external air conduit, in comparison with the case where the cylindrical port is housed in the recess. Moreover, the recess to be formed around the cylindrical port is no longer needed in this mode of the invention, making it possible to reduce the axial length of the first partition member by the axial length of the recess. Thus, the fluid-filled vibration-damping device can be made compact in its axial size.
(8) A fluid-filled vibration-damping device according to any one of the above-indicated modes (1)-(7), wherein the cylindrical portion of the second mounting member and the fixing cylindrical portion of the fixing member are fluid-tightly mounted onto respective portions of the outer circumferential surface of the first partition member with sealing rubber layers interposed therebetween over an entire circumference of the first partition member. The fluid-filled vibration-damping device of this mode of the invention permits a further improved fluid-tight sealing of the pressure-receiving chamber and the equilibrium chamber in an effective and stable manner.
(9) A fluid-filled vibration-damping device according to any one of the above-indicated modes (1)-(8), wherein the first orifice passage is formed at an outer circumferential portion of the first partition member so as to extend with a given circumferential length in a circumferential direction of the first partition member. This arrangement makes it possible to effectively obtain a length of the first orifice passage, thereby enhancing degree of freedom in tuning the first orifice passage. For instance, the first orifice passage may be formed in a spiral shape so that the first orifice member has the length that is larger than a circumference of the first partition member.
(10) A fluid-filled vibration-damping device according to any one of the above-indicated modes (1)-(9), wherein the first partition member has a groove open in the outer circumferential surface thereof and at least one of the cylindrical portion of the second mounting member and the fixing cylindrical portion of the fixing member fluid-tightly closing an opening of said groove so as to at least partially form the first orifice passage. This arrangement makes it possible to provide the first orifice passage with the reduced number of components, with effective utilization of the first partition member and the second mounting member or the fixing member.
(11) A fluid-filled vibration-damping device according to any one of the above-indicated modes (1)-(10), further comprises a second partition member, which is fixedly supported by the partition member, and which divides the pressure-receiving chamber into a primary fluid chamber partially defined by the elastic body and adapted to receive a primary vibrational load, and an auxiliary fluid chamber partially defined by the movable member, and a second orifice passage for fluid communication between the primary fluid chamber and the auxiliary fluid chamber.
The fluid-filled vibration damping device constructed according to this mode of the invention is capable of exhibiting a further improved active or passive vibration damping effect, on the basis of flows of the fluid through the second orifice passage. Described in detail, air pressure variation whose frequency corresponding to that of vibrations to be damped is applied to the working air chamber so that oscillation of said movable member is suitably controlled. This controlled oscillation of the movable member causes pressure variation of the fluid in the auxiliary fluid chamber that is transmitted to the primary fluid chamber, whereby the fluid-filled vibration-damping device can exhibit a high active vibration damping effect with respect to the vibrations to be damped, for example. In this case, the second orifice passage may be suitably tuned so that the fluid pressure variation is transmitted from the auxiliary fluid chamber to the primary fluid chamber with improved efficiency (hereinafter referred to as a xe2x80x9cpressure transmission effectxe2x80x9d), or so that high frequency components is reduced or minimized when the fluid pressure variation is transmitted from the auxiliary fluid chamber to the primary fluid chamber. Alternatively, a static air pressure applied to the working air chamber is suitable controlled according to frequencies of the vibrations to be damped so as to permit a selective use of the first and second orifice passages, or so as to change the tuning frequency of the second orifice passage. In this case, the fluid-filled vibration-damping device is capable of exhibiting the passive vibration damping effect on the basis of resonance of the fluid flowing through the second orifice passage with respect to vibrations having a plurality of frequencies or over a wide frequency range.
In this mode (11) of the invention, the second orifice passage may be preferably tuned to a frequency range that is substantially equal to an upper limit of the frequency range to which the fluid-filled vibration-damping device is expected to exhibit the active vibration damping effect on the basis of the oscillation of the movable member, so that it is effectively prevented that the high frequency component in the fluid pressure variation in the auxiliary fluid chamber is undesirably transmitted to the primary fluid chamber, when the fluid-filled vibration damping device is operated to exhibit the active vibration damping effect. In the case where the fluid-filled vibration-damping device is operated to exhibit its active vibration damping effect, the pressure transmission effect from the auxiliary fluid chamber to the primary fluid chamber is effectively improved with the help of the resonance of the fluid flowing through the second orifice passage in a frequency range to which the second orifice passage is tuned. Thus, the present fluid-filled vibration-damping device is capable of exhibiting further improved active vibration damping effect.